A Gnomon device would probably be a few hundred tons and a Sundial a few thousand tons - hence the delivery mechanism for the latter on Teller's blackboard apparently being "backyard":
With modern nuclear weapons design they could probably be a lot lighter. Speculation has it that the US can now build fusion secondaries without the heavy pusher.
https://blog.nuclearsecrecy.com/2012/09/12/in-search-of-a-bi...